Indigenous activists have called for urgent changes to Canada’s legal system after an all-white jury acquitted a white farmer of murdering a young Cree man in a case that has exposed deep racial divisions.

Gerald Stanley, 56, was found not guilty of second-degree murder over the death of Colten Boushie, 22, from Red Pheasant First Nation in the province of Saskatchewan.

Boushie’s family and aboriginal activists say the racial makeup of the jury underscored a weakness in the country’s court system, which allows defence teams to manipulate jury lineups in their favour.

Activists now hope to convert disappointment over Friday’s verdict into action to reform what they believe is a broken system.

“Today, we saw no justice,” Jade Tootoosis, Boushie’s cousin, said after the verdict. “We are angry, we are upset, and we are hurt. But we will continue to speak out for the injustices indigenous people face in this society. This is unacceptable.”

Boushie’s family has travelled to Ottawa to lobby ministers including Justin Trudeau, the prime minister, to bring changes to a system they feel deprived them of justice.

Trudeau has expressed dismay at the verdict. “I’m not going to comment on the process that led us to this point today, but I am going to say we have come to this point as a country far too many times,” he said on Friday.

Friends of the family have raised $85,000 in a crowdfunding campaign aimed at supporting the family and raising awareness of the challenges indigenous peoples face within the justice system.

“Watching the family go through the the trial, we all realized that the Royal Canadian Mounted Police and the Canadian justice system as it’s set up can’t bring us justice,” said Erica Violet Lee, a Cree activist from Saskatchewan who started the funding campaign. “The pressure’s on indigenous people to heal and to move on and forget the past. But the whole past is tied to this verdict.”

The case centered on the events of an August evening in 2016, when Boushie and a group of friends arrived by car at Stanley’s farm.

According to the prosecution, the group pulled into the farm after a flat tyre. The defence argued that they arrived with the intention of stealing an all-terrain vehicle.

After an altercation involving Stanley, his wife and son and Boushie, the farmer approached the vehicle and fired a pistol three times, the court heard. The last bullet struck Boushie in the head – an event Stanley later called a “freak accident”.

Activists say that the not-guilty verdict owed much to the selection of an all-white jury, even though Saskatchewan has a large indigenous population.

Under the current system, legal teams are allowed to weed out potentially hostile jurors with a “peremptory challenge” during jury selection.

In the Boushie case, the defence team systematically vetoed prospective jurors who were or appeared to be indigenous, said Tim Quigley, a law professor at the University of Saskatchewan.

“It was simply these peremptory challenges that resulted in no indigenous people at all on the jury,” he said.

Unlike Canada, the US and the UK have systems in place to prevent legal teams from keeping people off of a jury on discriminatory grounds, said Quigley, who also criticised other aspects of the police investigation as “appallingly bad”.

Officers failed to cover the vehicle in which Boushie’s body lay and bloodmarks were lost when it rained overnight.

A key element of Stanley’s defence was that there was a delay, known as “hang fire”, between his pulling of the trigger and the discharge of the weapon. Expert witnesses for both the prosecution and defence testified that the gun showed no indication of “hang fire” or any other malfunction.

In Canada, the use of a firearm is not permitted in order to defend private property. Even in self-defence – which Stanley did not claim – the use of lethal force is rarely permitted under the law.

It took the 12-person jury 27 hours to reach a verdict of not guilty.

“I’ve been a lawyer for more than 40 years and a law professor for 28 years, so I’m quite familiar with the criminal justice system. But while I knew an acquittal was possible, I wasn’t expecting this,” said Quigley, noting that negligence with a weapon should have resulted in a manslaughter charge.

An appeal court cannot overturn a jury acquittal, Quigley said, adding: “It will be difficult for the family to get in any sense of justice on Colton Boushie’s death.”

For indigenous activists, the focus is now on shifting attitudes in the legal system – and throughout the country.

For activists like Lee, the case presents a brief window for many Canadians to view a sliver of the injustices she argues indigenous people face daily.

“We looked up at the front of the court room and you could see everyone in charge of our fate was white.” said Lee. “And above it all, there is a picture of the Queen looking over the court room. We realized this is not a system set up for us: this is not a system set up to keep us safe.”